Road maintainer



July 27, 1943. M. F.' ALLEN ROAD .MAINTAINER Filed sept.y 11, 1940 4 Sheets-Sheet l R NN .hn hw hm. uN m f i TV MQ m@ M .k WM m u l m 1 r w. mw MW ,www -Q n .1 l mw uw m Q W m s mm. Q n ,I l N M s n N Mw. n 1 1 .8N 5m, NSN .W bm. f l, r e Nm V. .uw o f b\ B H l (l h M M "l I RN m m mh .NNN mm Qwl l T0 .w q NW f L 1 n \l, -Mm H l |m KN .x\. )Il w .v w I1 .3Q lvQN, m kk. QN bw w .MSN bw W \N\. Mm. la w N .MM Nk N Huhn? hHHuuuhwHuHuH/J n|| uw www NW .N .MWN

July 27 1943- M. F. ALLEN `2,325;025

ROAD MAINTAINER Filed Sept. 11,v 1940 4 Smets-Sheet 2 July 27, 1943.y M. F. ALLEN l ROAD MAINTMNER y Filed Sept. ll 1940 4 She-:etS-Shee.4

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Filed Sept. 1l, 1940 4 Sheets-Sheet 4 37 f .M 4 i 2, 0 m 7 T i 5 4 E E w o E M m Vm" E n E E D 0, f i A J a L l/ M 4 IIJ Iz l row/nys.

l YPatented July 27, 1943 `UNITED STATES PATENT OFI-TICE? 2,325,025 I l Y ROAD MAINTAINER Morris F.'Allen, Canton, Ohio Application september 11, 1940seria1No. 356,295

16 Claims.

My invention relates to road maintainers, and more particularly to road maintainers of the type in which front and rear blades, oppositely oblique, are supported for independent adjustment upon a pair of longitudinally extending skid-frames mounted at opposite sides of the vehicle. The principal object of my invention is to increase the flexibility of blade adjustment and to make it possible to adjust independently either end of either blade without introducing strains into the structure by which the blades `are interconnected and supported. A further object of my invention isto accomplish this result with a construction which can be simply and economically manufactured and which will be sturdy and durable in use. Another object of my invention is to improve the maintainer construction set forth and described in my co-pending application Serial No. 355,439, filed September 26, 1940.

In carrying out my invention, I employ ar wheel-supported main frame which serves as a support for the operator and 'for the blade` adjusting mechanism, and through Whichrthe blades are drawn. The two blades are mounted in op-positely oblique relation upon two skid frames vwhich are disposed at the sides of vthe il me and which, when the machine is in. operation, are in Contact with the ground and support the blades.` Each end of each blade is mounted for independent vertical adjustment upon the adjacent skid fra-me; and the two blades are'arranged so that loose earth on the surface of the road will pass successively along the blades 'as the machine is operated. Near one side of the machine eech blade is connected on ahorizontal transvei e axis to a sub-frame, and near the other side of the machine thetwo blades are connected on horizontal transverse axes' to a spacing member which, at an intermediate point, ispivotally connected to such sub-frame.' Draft 'le rapplied to the unit comprising the two skid frames and the two blades by draw-bars the iront ends of which are connected to the main frame and the rear ends of which. are pivotally connected near opposite sides of the machine to e spacing member and the sub-frame respec-l (o1. 27g-15o) The accompanying drawings illustrate'my invention: Fig. 1 is a plan View of the machine; Fig. 2 is an elevation of the left side of the machine; Fig. 3 is' a vertical longitudinal section on the line 3-3 Vof Fig. 4 showing the blades in side elevation; Fig. 4 is a plan view of the blades and blade-interconnecting structures; Fig. 5 is a fragmental l plan View illustrating a stone-thrower, which is disposed at the rear end of the righthand skid frame; Fig. 6 is a rear elevation with parts of the machine brokenA away in various planes and shown in section; Fig. 7 is a diagrammatic view ofthe hydraulic adjusting mechanism; Fig. 8 is'a vertical section through the blade-mountingemployed at the right-hand end of the front blade; and 9 is a section on .the une s-s of Fig. 8. f

As'will be clear from Figs. 1 and 2, the machine comprises a main `trame l5 which is supported at its rear end upon rear wheels I6 and at its front end upon front Wheels l1. The front wheels Il' are mounted at the ends of a transverse axle on' a iront truck I8 which is pivoted yto the main frame on a vertical axis to permit steering movements and which is provided with ak draft-tongue i9 adapted'for connection to a tractor, truck, orother source of draft effort.

At each side of the main frame there is disposed a skid-frame 2S which is generally trusslike in construction and which embodies an elongated ground-engaging runner 20. The two skidfrarnesa're desirablyinterconnected as by means of cross-members 2l which may be disposed at' any convenient points.

Extending longitudinally at each side of the main frame l5, I support therefrom arock-shaft 25 having at its ends crank arms 26 connected to the: adjacent skid-frame by links 2l. One end, desirably the upper end, of each of such links is slottedA soas to provide a certain amount of lostmotion in a vertical direction betweenY theV main frame l5 'and the skid-frame assembly. As a result of thisor as the result of lost-motion otherthe rm end of the skid-frame assembly laterally ln frame, while not interfering with Itical movement of the skid frame and main frame.

Near the longitudinal center of the left-hand skid frame I mount two pairs of parallel vertical guide-posts 3| and 32. See Figs. 2 and 4. The front pair of guide-posts 3| serve to support for vertical sliding movement a bracket 33 to which the left-hand end of the front scraper blade 34 is connected in a manner to be more fully described hereinafter'. The rear pair of guide-posts 32 support for vertical sliding movement a second bracket 36 to which the left-hand end of the rear blade 31 is connected.

Two similar pairs of guide-posts 46 and 4| (Fig. 4) are arranged on the right-hand skid frame, the guide-posts 40 being disposed near the front end of that skid frame and serving as a slidable support for a bracket 42 to which the right-hand end of the front blade 34 is connected. The pair of guide-posts 4| are mounted near the rear end of the right-hand skid frame and slidably support a bracket 43 to which the right-hand end of the rear blade is connected.

. The front and rear blades 34 and 31 are interconnected by a sub-frame 45 comprising an elongated longitudinal member 46 which has its ends bent downwardly and pivo-tally secured to ears 41 on the rear faces of the respective blades, the member 4 6 being located near the right-hand ends of the blades. The sub-frame 45 extends transversely toward the left-hand end of the blades and has its left-hand end pivotally connected on a horizontal transverse axis as by a bolt 48 to an intermediate point on a space-bar 49, which is similar to tbemember 46 in that its ends are downwardly bent and pivotally connected to ears 56 on the rear faces of the respective blades. Desirably, the pivotal connections between the ends of the members 46 and 49 and the ears on the blades are not single-axis connections but instead possess some freedom of universal movement, as by being of the ball-and-socket type. This type c-f connection, coupled with the fact that the space-bar 4S is pivotally connected to the sub-frame 45, makes it possible for the ends of the two blades to be independently adjustable into non-coplanar relationships without creating undue strains in the assembly embodying the subframe, the blades, and the space bar 49.

For the purpose of applying draft effort to the assembly of blades and skid frames, I employ draw bars 55 pivotally connected on a transverse axis at their front ends to a yoke 56 which is secured to and extends downwardly from the main frame |5. The rear ends of the two draw bars are pivotally connected respectively to the space bar 49 and to the opposite side of the sub-frame 45, as by pivot bolts 51.

To control the pitch of the blades, or the angular position of each about the axis of its connection to the members 46 and 49, I employ pitch links B6. Each of these pitch links is pivotally connected to its associated blade near the upper edge thereof, and the two links extend toward each other and have their adjacent ends pivotally connected to the sub-frame 45, conveniently on a common axis, as indicated at 6|. To avoid strainwhen the blades are independently adjusted, the connections at the ends of the pitch links are desirably ball-nnd-socket connections.

It will be apparent that differences in the respective elevations of the front and rear blades will involve variation in the horizontally pro,- jected lenghts of the members 46 a-nd 49 through which these blades are interconnected, and that accordingly provisions should be made for relative movement of the two blades longitudinally of the machine. In addition, since the pitch of the blades is fixed relative to the sub-frame by the pitch links 69, changes in the relative elevations of the blades will entail a certain amount of rocking movement of each blade relative to the skid frames. These different movements of the blades are desirably provided for by the means employed to connect the ends of blades to the brackets 33, 36, 42, and 43.

As will be clear from Figs. 1 and 4, the rear blade 31, which extends from one skid frame to the other, is provided at its ends with rearwardly extending ears 65 which are pivotally connected respectively to vertical flanges 66 on the brackets 36 and 43, desirably by pivot bolts 61. The pivot bolts 61 are located approximately in continuations of the straight line between the ball-andsocket joints at the rear ends of the members 46 and 49, but the axes of the bolts 61 need not be co-incident with that straight line. In fact, I prefer to dispose each of the pivot bolts so that its axis will be substantially normal to the vertical plane of its associated skid frame, making the bolt-receiving holes in the ears and flanges 63 large enough so that no undue binding will occur if the two ends of the rear blade are at different elevations.

At its right-hand end, the front blade 34 is provided with a rearwardly extending ear 1D on the outer face of which is secured a boss 1| (Fig. 8) received for sliding movement longitudinally of the machine in a guide member 12 rigid with a vertical flange 13 on the bracket 42. The ear 16 and boss 1| are pierced, and the guide member 12 and flange 13 are slotted, for the reception of a bolt 14 which retains the ear 10 in association with the bracket 42. As shown in Fig. 9, the boss 1| has top and bottom faces which converge outwardly and slidably engage the complementarily inclined side walls of a groove in the inner face of the guide member 12. Desirably, the bolt 14 has associated with it a compression spring 15 which acts between the nut on the inner end of the bolt and the inner face of the ear 1|! and resiliently holds the inclined faces of the boss 1| in contact with the mating faces of the guide member 12.

The left-hand end of the front blade is spaced inwardly from the adjacent skid frame to permit the passage of loose earth to the rear blade. To connect the front blade to the vertically slidable bracket 33 on the left-hand skid frame, an arm 16 rigid with the blade projects outwardly therefrom and is provided with a continuation which projects rearwardly into association with a vertical fiange 11 on the bracket 33. The arm 16 is connected to the flange 11 through a boss 1|, guide member 12, bolt 14, and spring^15 similar to the correspondingly numbered parts at the righthand end of the front blade.

The springs 15 serve normally to force the inclined faces of the bosses 1| into contact with the inclined faces of the grooves in the guide member 12 and thus to hold the front blade in fixed angular position about the axes of the bolts 14. However, when the difference in elevation of the front and rear blades is extreme, the front blade may rock about the bolts 14, rotating each boss 1| relative to its associated guide member.

VThis action is permitted by reason of the fact that the engaging faces of the boss and guide member are inclined to the bolt-axis, such faces acting as co-operating cam surfaces forcing the rear ends of the ear and arm 16 inwardly and stressing the springs as the front blade rocks. In order to avoid too great opposition to rocking movement of the front blade, the ends of the inclined faces of the bosses 1| may be relieved as indicated at 18 in Fig. 9.

With the construction described, draft efforty is applied to the skid frames through the draw bars 55, sub-frame 45 and space-bar 49, rear blade 31, pivot bolts 61, brackets 36 and 43, and the guide rods 32 and 4|, Because of the longitudinally slidable connections between the' front blade and the brackets 33 and 43, the front blade and its connections to the skid vframe convey noy draft eilort to the skid frames. This is of advantage in effecting automatic control of the elevation of the front blade in the manner hereinafter described.

The various adjustments of which the machine the front truck and Awhich projects upwardly through al longitudinal slot |00' in a bolster |0| is capable, including the independent adjustment Y of each end of each blade relative to the skid frames-and the raising of the skid frames and.

blades as a unit relative to the main frame, ma;y be effected in any desired manner. I prefer, however, to eiiect such adjustments by hydraulic mechanism and to include in the adjusting means the device set forth in my co-pending application Serial No. 353469 for exercising an automatic regulation of the height of the front blade in accordance with the magnitude oi the earth reaction of the blades. Y y

In providing for hydraulic adjustment of the blades in the'skid frames, I associate with each of the brackets 33, 36, 42 and 43 a pair of tension springs 00 which act between the bracket and the associated skid frame tending to move the former upwardly on the-guide posts Yon which it is mounted Ahydraulic jack 8|, acting between each of the brackets and its associated skid frame tends'to force the bracket downwardly in opposition to the springs 30; A maniiold 82 located on the main frameV I5 is connected through conduits 83 to the jacks 8| at the ends of the ,front blade, each of such conduits including a valve 84. A second pair ofconduits 85, each containing a valve 86, connect the manifold 82 with the jacks at theV ends of the rear blade. A pump 81, mounted on the main frame and conveniently adapted for manual operation by an operator standing on an operators platform 88, receives liquid from a supply tank 89 and delivers it to the manifold 82. A return conduit 8D, including a valveill, interconnects the manifold 82 and tank 59 independently of the pump. j

Ther means for automatically controlling the elevation of the front blade in accordance with earth reaction comprises two hydraulic cylinders 95k disposed longitudinally of the machine and desirably located near the front end thereof in side-by-side relation. in each of the cylinders B5 is a piston 86 whichv projects forwardly from the cylinders; and the rear ends of the two cylinders are connected respectively to the two conduits 83 by lines 33 so thatv pressure in such conduits will tend to move the pistons 95 forwardly in the cylinders 55. Forward movement of the pistons is limited, however,l by their engagement with a cross-arm 91 on a member 98 which is longitudinally slidable in the main frame |5. The iront truck I8 is .also capable of longitudinal movement relative Vto thev main frame as by being connected thereto through the medium orv a king-pin |00 whichis rigid with at the front end of the main frame. The front end of. the member 98 is connected to the kingpin |00 to be movable longitudinally of the main frame with the front truck, and is urged rearwardly as by a compression spring |02 normally to holdthe king-pin |00 vat the rear end of the slot |00. The force with which the spring |02 actsto hold the front truck and king-pin at the rearward limit of their movement relative tothe main frame l5 may be varied by adjustment of a, nut |03 which is screw-threadedly mounted on the member 98 and against which the spring |02 acts.

When the machine is in operation, the skid frames are in vvcontact with the ground and the elevation of each end of each blade depends upon the quantity of liquid `in the associated jack 8|. To increase the' quantityl of liquid in any jack, and thereby lower the adjacent bladeend, the valve (84 or 86) in the conduit leading to that jack is opened andthe pump 81 operated to displace liquid from the supply tank B9 into the jack, and when the blade-end being adjusted has been lowered to the desired extent operation of the pump is stopped and the valve is closed, To reduce the quantity of liquid in any jack, and thereby raise the adjacent blade-end, the valve in the conduit leading to that jack and the by-pass valve 9i are both opened, thus permitting the return ofliquid to the supply tank under the influence of the springs 80. Closing of either of the valves just referred to will stop liquid return and interrupt raising movement of thel blade-end.

It will be noted that with the front blade in any position of vertical adjustmentl the springs associated with ,the front jacks will create a fluid pressure in the conduits B3 and in the cylinders 95. Such fluid pressure acting on the pistons 96 will force ythemforwardly into engagement with the cross-arm 91 on the member and will tend to move that member forwardly. The spring |02. will oppose such forward movement of the member 93, and the spring is of such capacity and the nut |23 is so adjusted as to prevent movement of the member 9B as the result ofany fluid pressure occurring in the use of the machine. In consequence, control of the front jacks by operation of the pump t1 and manipulation of the valves 84 and 9i vestablishes a definite normal vertical elevation for each end of the front blade'. Should earth-reaction on the blades become so great that the'draft-eiiort-.Y 'ransmitted to the main frame i5 r'through the member 9Sk and spring |02, wili compress the spring, the member 38 (and the cross-arm 91 rigid fwith it) will move forwardly permitting forward movement of the pistons' and disifvl'acementl of Vliquid fromthe front jacks into the cylinders 35, and consequent rais ci both ends of the front blade, under the i l the springs ii associated therewith Re the front blade will reduce the inagn' earth-reaction upon it, and will acc-a ,ly decrease draft effort. As a result, the draft effort may always be maintained below a predetermined maximum with the attendant advantages set' forth in my co-pending application above referred to.l

When the machine is out performing any earth-working operation, the rock-shafts'ZS are rocked to elevate the assembly of skid frames and blades clear of the ground.

to be transported witl -V This is conveniently done by providing the rockshafts respectively with operating arms |05 connected by flexible tension members |06 to a hydraulic jack |01 on the main frame I5. The jack |01 is connected to the manifold 82 through a. conduit |08 which contains a valve |09. With the by-pass valve 9| closed and the valve |09 open, operation of the pump 81 will displace liquid from the supply tank into the jack |01 to rock the shafts 25 and elevate the skidv frames. If the vaives 9| and |00 are both opened liquid will return from the jack |01 to the supply tank underrthe iniiuence of the weight of the skid frame and the blade assembly as it settles into contact with the ground.

In the actual operation of the maintainer, the front blade will usually be set so as to cut o and loosen at least the high spots of the road over which the maintainer is being drawn, and the earth thus loosened will proceed rearwardly to the left along the front blade, passing around the left-hand Vend thereof to the rear blade. Ordinarily, the rear blade will act merely as a distributor of the loose earth delivered to it from the front blade and will perform no scraping function. In certain instances, however, the left-hand end of the rear blade may be set low enough to perform some scraping. The righthand end of the rear blade will almost always be set at an elevation sufliciently high to permit all the loose earth to pass beneath it, so that no loose earth will be left to accumulate in front of the right-hand end of the rear blade or to pass around such end to leave a windrow.

As a result of the fact that the primary function of the front blade is to scrape while the rear blade performs little if any scraping, by far the larger part of the total rearward earthreaction on the blades is exerted on the front blade and is dependent in magnitude upon the elevation of the front blade. Accordingly, the automatic control of blade elevation in response to rearward earth-reaction, which control is exerted through the mechanism including the cylinders 95, pistons 5,6, members 98, and spring |02, need operate only on the front blade. By making the adjustment of both ends of the front blade entirely independently of adjustments of the rear blade, in contradistinction to the machine shown in my co-pending application above referred to in which a single adjusting mechanism controls the elevation of the left-hand end of both blades, the automatic control does not affect the adjustment of either end of the rear blade, and hence does not interfere with the action of the rear blade in producing a smooth, and even surface on the distributed earth.

To prevent the accumulation at the right-hand end of the rear blade of stones too large to pass beneath the lower edge of that blade, the lower right-hand end of the blade may be cut away as indicated at ||2 in Fig. 5. Near the rear end of the right-hand skid frame 20 I mount a deflecting member ||3 which is obliquely disposed and which extends outwardly beyond the rear end of such skid frame to deect outwardly any stones passing through the opening ||2.

I claim as my invention:

l.. In a road maintainer, a wheel-supported main frame, a pair of ground-engaging skid frames disposed longitudinally at the sides of said main frame, a pair of scraper blades extending in oppositely oblique directions between said skid frames and supported for vertical adjustment thereon, means for independently adjusting each end of each of said blades, a subframe disposed beneath said main frame, said blades near their more widely spaced ends being pivotally connected to said sub-frame on axes extending transversely of the maintainer, a space-bar pivotally connected at a point intermediate its length to said sub-frame on an axis transverse to the maintainer, sad blades near their less Widely spaced ends being pivotally connected respectively to opposite ends of said space bar, and means for conveying draft eiort from said main frame to said skid frames and blades.

2. The invention set forth in claim l with the addition that said draft-conveying means comprises draw bars connected at their front ends to said main frame and at their rear ends to said sub-frame and space-bar respectively.

3. In a road maintainer, a wheel-supported main frame, a pair of ground-engaging skid frames' disposed longitudinally at the sides of said main frame, a pair of scraper blades extending in oppositely oblique directions between said skid frames and supported for vertical adjustment thereon, means for independently adjusting each end ci each of said blades, a pair of members extending longitudinally of the maintainer between and pivotally connected to said blades near opposite ends thereof, means pivotally interconnecting said members on an axis between their ends, and means for conveying draft effort from said main frame to said skid frames and blades.

4. The invention set forth in claim 3 with the addition that said draft-conveying means comprises draw bars connected at their front ends to said main .frame and at their rear ends to said blade-connecting members respectively.

5. The invention set forth in claim 1 with the addition of a link extending between each blade and said sub-frame and connected to the associated blade near the middle of the length thereof for controlling the position of each blade about the axis of its pivotal connection to said subframe and space bar.

6. In a road maintainer, a ground-supported, blade-supporting structure, a pair of scraper blades supported for vertical adjustment from said structure and disposed in oppositely oblique positions, means for independently adjusting each end of each of said blades, a sub-frame, said blades near their more widely spaced ends being pivotally connected to said sub-frame, and a space-bar pivotally connected at a point intermediate its length to said sub-frame on an axis transverse to the maintainer, said blades near their less widely spaced ends being pivotally connected respectively to opposite ends of said spacebar.

7. The invention set forth in claim 6 with the addition of a link extending between each blade and said sub-frame and connected to the associated blade near the middle of the length thereof for controlling the position of each blade about the axis of its pivotal connection to said subframe and space bar.

8. In a road maintainer, a ground-supported, blade-supporting structure, a pair of scraper blades supported for vertical adjustment from said structure and disposed in oppositely oblique positions; means for independently adjusting each end of each of said blades7 a pair of members extending longitudinally of the maintainer between and pivotally connected to said blades near Opposite ends thereof, and means pivotally interconnecting said members on an axis between their ends.

9. In a road maintainer, two laterally spaced, longitudinally extending skid frames, a pair of scraper blades extending between and supported for vertical adjustment on said skid frames, mechanism for independently vertically adjusting each end of each of said blades, draw bars, and means connected to said draw bars for conveying draft effort from the draw bars to said blades independently of Ysaid skid frames, said means including a plurality of members connected to said blades and movable relatively to each other to permit independent adjustment of the blades.

l0. In a road maintainer, two laterally spaced, longitudinally extending skid frames, two brackets mounted on each of said skid frames in longitudinally spaced relation and adapted for vertical movement relatively thereto, means for independently adjusting each of said brackets vertically, a rear blade extending between said skid frames and pivotally attached to the rear brackets thereon, a front blade extending between said skid frames and attached to the front s thereon for movement both pivotally a longitudinally of the maintainer, draw bars,

means connected to said draw bars forconve draft effort from the draw bars to said blades independently of said skid frames, said means including a plurality of members connected to said blades and movable relatively to each other to permit independent adjustment of tie blades.

l1. In a road maintainer, two laterally spaced, longitudinally extending skid frames, two brackets mounted on each of said skid frames in longitudinally spaced relation and adapted fory vertical movement relatively thereto, means for independently adjusting each vof saidl brackets vertically, a rear blade extending between said skid frames and pivotally attached to the rear brackets thereon, a front blade extending between said skid frames and attached to the front brackets thereon for movement both'pivotally and longitudinally of the maintainer, a pair of members extending longitudinally of the maintainer between and pivotally connected to said blades near opposite ends thereof, means piv- `otally interconnecting said members onan axis intermediate their ends, and means for applying draft eort to said blades, said means including draw bars pivotally connected to said members respectively.

12. In a road maintainer, two' laterally spaced, longitudinally extending o 'Ll skid frames, two brackets mounted on each of said skid frames in longitudinally spaced relation and adapted for vertical movement relatively thereto, means for independently adjusting each of said brackets vertically, a rear blade extending between saidV skid frames and pivotally attached to the rear brackets thereon, a front blade extending between said skid frames and attached to the front brackets thereon for movement both pivotally and longitudinally of the maintainer, a pair of members extending longitudinally of the maintainer between and pivotally connected to said blades nearopposite ends thereof, and means Vpivotally interconnecting said members on an axis intermediate their ends.

13.111 a road maintainer, a ground-supported, blade-supporting structure, front -and rear scraper blades mounted on said structure for vertical adjustment, means for independently adjusting said blades vertically, and automatic mechanism responsive to rearward earth reaction on sai-:l blades as the maintainer moves over the ground for raising the front blade independently of the rear blade to an extent dependent upon the magnitude of such earth reaction.

14. In a road maintainer, a ground-supported, blade-supporting structure, front and rear scraper blades mounted on said structure for vertical adjustment, means for independently adjusting each end of each of said blades vertically, and automatic mechanism responsive to rearward earth reaction on said blades as the Vmaintainer moves over the ground for raising both ends of the front blade independently of the rear blade to an extent dependent upon the magnitude of such earth reaction.

15. The invention set forth in claim 14 with the addition that the means for adjusting each end of said front blade comprises a hydraulic jack, said automatic mechanism comprising a device to vary the pressure in said jacks to an extent dependent upon the force required to pull the machine over the road surface.

16. In a road maintainer, a ground-supported, blade-supporting structure, a rear blade extending transversely thereof and mounted in fixed longitudinal position thereon, a front blade extendingV transversely of said structure and movable both vertically and longitudinally relative thereto, means interconnecting said two blades,

a draw bar for`applying draft effort to said blade y Yextent dependent upon the magnitude of such earth reaction. v

MORRIS F. ALLEN. 

